5.7 The role of the lymphatic system

what is the lymphatic system?

consist of a network of lymphatic organs that transport organs and vessels that transport fluid, wastes, immune cells and pathogens around the body and back into the bloodstream. Interstitial fluid surrounds the bodies cells and lymph issues fluid drained by lymph nodes

what are the primary lymphatic organs or tissues?

• Bone marrow is the sponge middle part of the bone where immune cells are produced.

immune cells that remain in the bone marrow mature into B cells

• Thymus the immune cells that move from bone marrow to th thymus into T cells

what are the secondary lymphoid organs or tissues?

• lymph nodes collect and filter lymph fluid drained from the body as it travels along lymph vessels, trapping foreign materials anywhere lymphocytes can come across antigens and response to them (using inflamed lymph nodes)

• the spleen is a dark blood-filled organ that filters the blood, removes old red blood cells, detects foreign invaders and produces antibodies

what are the cells involved in the adaptive immune system?

• antigen presenting cells

• helper T cells

• B cells

• cytotoxic T cells

what is self-tolerance?

the inability of an adaptive immune system to respond to the bodies own self antigens

what are lymph nodes?

Lymph nodes are the site of antigen recognition, in which T and B lymphocytes come into contact with their specific antigens. This results in clonal selection and expansion.

what does it mean if a cell has a letter next to it?

if it has the T or B with its name its a lymphocyte

What are antigen presenting cells?

once am APC such as a centric cell engulfs.a pathogen, it presents an antigen from this pathogen on the MHC - II markers on the outside of the outside of cell and moves to the lymph nodes to meet with helper T cells

what are helper T cells?

helper T cells are involved in kickstarting one of the two adaptive immune pathways

• cell-mediated and humoral

what occurs in B cells (humoral immune response)?

after clonal selection and expansion of naive B cells, the naive B cells differentiate into:

• memory B cells - contains the same antibody as the original B cell, but lasts for long periods of time

• plasma cells - produced and releases large amount go antibodies which clumps around viruses

what occurs in antibodies (immunoglobulin) in humoral immune response?

proteins created by plasma cells involved in the immune system that consist of the 4 polypeptide chains - two heavy (long) and two light (short) - which have two binding sites which bind to specific foreign

what are the two binding sites which bind to specific foreign antigens in humoral immune response?

• constant region - the same in every antibody

• variable region - unique to a specific antibody and contains the antigen binding site

what are antigen-antibody complexes in humoral immune response?

once the plasma cells produce antibodies. they bind to the specific antigens present in the body, inactivating the pathogen and attracting phagocytes to eat the pathogen

what are the cytotoxic T cells in the cell-mediated immune response?

cells that travel around the body to signal infected cells to undergo apoptosis by realising a death ligand

what are lymphocytes

(same as leukocytes/white blood cells) which detect invading pathogens and initiate an immune response

what are plasma b cells?

fires large amounts of antibodies at a specific antigen. Contains lots of Golgi apparatus and rough endoplasmic reticulum to help with production.

short lived

what are memory b cells?

has receptors specific to a type of antigen and remembers it. When stimulated, it differentiates into plasma B cells and more memory B cells.

Long lived

what are regulatory T cells?

turns off the activity of immune cells by secreting signalling molecules and cytokines

what are suppressor T cells?

surprises T and B cells at the end of the response to infection

what are memory T cells?

remembers a certain antigen to provide long-term immunity for future infections by that pathogen

what are B lymphocytes?

produced and matured in bone marrow and travels to the spleen and lymph nodes. It produces antibodies, which bind to a specific epitope on the surface of pathogens, labelling it for engulfment and destruction by macrophages.

Works in blood and lymph (extracellular pathogens - outside cells).

B cells are antigen presenting cells (APCs).

what are T lymphocytes?

produced in bone marrow and matures in the thymus. They don't have antibodies. Work within cells infected by pathogens (intracellular pathogens - within cells).